This can be done as Snake or Raiden and in numerous places throughout the game. In certain lockers are pinups of girls on the inside part of the locker door. Go inside the locker and close the door, angle your view down to the poster and firmly press to zoom in on the poster and then let go. While it zooms in and out you should hear a smooching noise, do it correctly and you'll earn this trophy. The earliest possible time to get this trophy is as Snake in the area Deck-A, Crew's Quarters.

You can also do this trophy in the Snake Tales mission "External Gazer" If you do this mission before you start the story, the mission will make you go to the Dinning Hall in Strut C and there is a poster of a female in the women's bathroom in one of the bathroom stalls. I did this mission before starting the story and got the trophy immediately after kissing the poster.